Liquidity and Shorting

Greetings everyone, I hope someone can help me understand the order execution differences between shorting/buying in terms of timing of execution.

Scenario - I wanted to Short MSFT, according to Nasdaq, their last reported short interest was around 95M. Let's say I put in a market order for the short. Is there a difference in fill time between that order, and one where I wanted to go long on MSFT at the exact same time?

Which would fill first and why? I'm sure it's a simple answer for some, but I appreciate the knowledge sharing.